Pathways
The images on the nasal sides of each retina cross over to the opposite side of the brain via the optic nerve at the optic chiasm. The temporal images, on the other hand, stay on the same side. This allows the images from either side of the field from both eyes to be transmitted to the appropriate side of the brain, combining the sides together. This allows for parts of both eyes that attend to the right visual field to be processed in the left visual system in the brain, and vice versa. This is linked to skin sensation which also reaches the opposite side of the body, after reaching the diencephalon (rear forebrain). This decussation (crossing) is an adaptive feature of frontally oriented eyes and therefore having binocular vision. (Some animals, with laterally positioned eyes, have little binocular vision, so there is a more complete crossover of visual signals.)
Beyond the optic chiasm, with crossed and uncrossed fibers, the optic nerves become optic tracts. The signals are passed on to the lateral geniculate body, in turn giving them to the occipital cortex (the outer matter of the rear brain).
Read more about this topic: Optic Chiasm
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